This study will develop and implement a cross-sectional evaluation of the exposure to fluorides of adolescents living in nonfluoridated or fluoridated communities and the dental caries and fluorosis status of these individuals. The general objectives of the study are: to quantify fluoride exposure of individuals in both fluoridated and nonfluoridated communities; to establish individual variation and response to fluoride exposure by estimating fluoride distribution in body fluids and tissues, as well as disease and tissue expression (dental caries and fluorosis); to correlate the fluoride levels from different body fluids and tissues with each other and with reported current intake, past fluoride experience presenting as dental fluorosis, and dental caries experience; and to contrast these relationships in fluoridated and nonfluoridated communities and between groups of individuals with different fluorosis manifestations.